Locknuts, Lock Washers , Loctite

[mobiledynamics]

So I'm building a unistrut frame to be bolted on my roof where my mechanicals are....rod anchors on anchors holes, etc....

Just short of a bolt being torqued enough that it shouldn't back out, and I plan to just use a lil blue loctite here and there. Got me thinking. What applications would you choose a locking washer or nyloc, over loctite

 

[bmwpowere36m3]

Threadlocker works well in blind holes, when you don't have access to put on a locking nut. Locking washers don't really work, yet we can't stop using them. I'm guilty of it as well.

Threadlocker and nylocs can breakdown from high heat. In some applications they are interchangeable.

 

[cvairwerks]

Self locking nuts, such as Nylocs, are used in high vibration, but little or no motion instances. Where there is motion, external locking is used...cotter keys, deformation washers, safety wire or cable, locking plates ect.

 

[fordnut85]

As stated before, loctite for threaded holes. My preference is mechanical locknut's over nylocks since using power tools with nylocks tends to degrade their effectiness.

Sent from my Pixel using Tapatalk

 

[kbuhagiar]

This is a great topic for discussion.

I've often wondered about the usefulness of split or serrated lock washers.

It would be interesting to hear from those with actual experience about what works and what doesn't, what to use, correct applications, etc.

FWIW, a brief Google search on the subject turned up, amongst many other results, this 100-page fastener-design research paper from NASA. Interesting.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf

 

[kams1973]

Nord lock washers are expensive,but they work well. I prefer lock washers or lock nuts for items that need to be removed from time to time. If it's considered a permanent install and heat is not a factor, thread locker is my choice.

 

[rlitman]

Blue (i.e. removable) theadlocker has one advantage. It seals the threads, so it will prevent corrosion. I've used it in places where I would otherwise have to use anti-seize.

 

[earlthegoat2]

Unless it is an exceptional circumstance, I only use locking nuts of some type. I rarely use threadlocker or find myself needing to but it does get used still. Im a fleet manager and when I am taking something apart and it has regular nuts and/or lock washers I replace them with a locking type every time.

I am also preferential to the flanged types of lock nuts as well so I do not need a separate washer most of the time during those applications that call for one. If companies would just use more locknuts instead of a standard nut and lock washer they could cut down on manufacturing costs for materials used. I have priced out in various ways the cost of installing a flanged nylock instead of a washer, nut, and lock washer combo. It is nearly half as much. Often, it is only fractions of a penny more to use a lock nut instead of a standard nut. Sometimes it is less even. Flanged nuts are marginally more but still a much better and less expensive option than the washer, nut, lock washer combo. Maybe it is a manufacturing thing though.

I have observed this though. On higher priced brands of equipment they tend to use more locking flanged nuts and serrated flanged bolts than the brands of lower priced equipment which will use more standard nuts and lock washers and standard bolts and screws.

 

[skruft]

Good comments.

There have been articles saying split lock washers are no good. I think they are fine as long as there is not a lot of movement, or even if there is, if the holes are the right size.

 

[DFB]

I chose to use serrated flange nuts to safety secure the custom saddlebag mounting on my motorcycle, a threaded bolt thru a U clip with caged nut.

Vibrations would sometimes work them loose on long non stop rides Has worked out great never loosens up or backs itself off plus no separate washers to fumble around with and is just so much easier to remove and install than using any nylock nut.

A liquid threadlocker just isn't a good option here with all the frequent detachment.

 

[Provincial]

Proper torque is a major factor in fasteners staying put. If the fastener is tightened properly, and the joint is not overstressing the fastener, they rarely work loose. If properly torqed fasteners loosen in use, the joint is improperly designed. Either the fasteners are too small, too few, too weak, or the joint itself is not designed to take the forces it experiences.

 

[earlthegoat2]

Proper torque is a major factor in fasteners staying put. If the fastener is tightened properly, and the joint is not overstressing the fastener, they rarely work loose. If properly torqed fasteners loosen in use, the joint is improperly designed. Either the fasteners are too small, too few, too weak, or the joint itself is not designed to take the forces it experiences.

I agree one hundred percent with this assessment.

I tend to think if everything was designed to that level of detail then mechanical objects would have less problems in general and fasteners would become a very moot point indeed. Having submitted written reports and reviews of problems on newer equipment to the companies we purchase from, I can tell you that well thought out design to the level you are stating is not happening quite often and details that maybe should never arise, such as fasteners, are becoming the crutch that said questionable designs are leaning on to pull them through said design problems. Fasteners cannot replace a well designed joint for the stresses involved and things like Loctite and locking washers and nuts help them limp along.

 

[Coach James]

https://engineerdog.com/2015/01/11/10-tricks-engineers-need-to-know-about-fasteners/


Coach

 

[mbshop]

One thing I started noticing looong ago was that washers of any kind were not fitting bolts or studs properly. The holes are just to big so the contact of the nut to washer is not good. Go look at your supply and notice the slop. So now the contact area is minimal and the pressure applied is waaay uneven. Hate to ssy it but this started when all the hardware started coming from china. Many of the so called sae sizes were actually metric. I noticed this when getting stuff for home use while I was still working on mercedes vehicles . The contact surface was totally off. There was a mix when I first noticed this and would scrounge for proper fitting washers, etc. No longer. So with sloppy surface contact, the idea of proper torque and holding surface contact goes out the window no matter what you are using. Just go look, certainly dropped my jaw.

 

[L5wolvesf]

This is a great topic for discussion.

I've often wondered about the usefulness of split or serrated lock washers.

It would be interesting to hear from those with actual experience about what works and what doesn't, what to use, correct applications, etc.

FWIW, a brief Google search on the subject turned up, amongst many other results, this 100-page fastener-design research paper from NASA. Interesting.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf

Great link, I'm going to have to study it. Here is a site I came across recently regarding fastening.

http://www.boltscience.com/

 

[DFB]

Ahh its always interesting what certain designers spec for....

When I did mechanical assembly of different power transformer "racks" as they were called back in my early factory days we had had many different types of lockwashers internal and external tooth, split lock, belville spring , even captive nut and washer combos each type called out for a different application. For the most part bolt thread was always UNC but sometimes a few were UNF too.

I will agree with the what was mentioned about getting an oversized inner dia. fitment on a lot of cheap washers especially with bulk purchase of flat these days.

 

[rsanter]

Split lockwashers are the most useless thing ever.
For them to work at all the nut has to start backing off a bit.
There are good lockwashers like the star type that will bite into the the surface of the nut and cause greater resistance to backing off. Only good for general purpose use not high stress or engineering applications.
They make locking nuts that are great. There are the nylocks as well as the type where the nut is crimped a little. Good for general purpose but not for applications where you have to torque to spec.

Bob

 

[sberry]

We quit using lock washers, way to many crack. I use a lot of flat under the turned element. For common hardware, we simply use a nut unless we want to spread the stress out, a common structural hole may be 20 percent over in lotso cases.

 

[theoldwizard1]

Self locking nuts, such as Nylocs, are used in high vibration, ...

Years ago, I learned that when working on outdoor power equipment that I want to last is would replace every nut, bot, washer with stainless steel and I always use Nylocs. Heck, you can even get "thin" stainless Nylocs !

 

[Leaflessshadetree]

Uni-strut frame on a roof. I'd use flat washers and regular nuts.
No lockwashers, loctite or locking nuts of any kind.

I use lock washers in low vibration applications where tightening torque is limited (for example plastics).
Loctite in blind holes.
I don't use a lot of locknuts. Usually nylon locking nuts in applications with vibration and mechanical where rotation is involved.

 

[sberry]

Lots of difference between holding some unistrut to hold an electric panel and a head bolt. Difference between the strut and high strength structural connection where a well fitting hard machine washer is used. Holding a fender on is another matter. Lots of apps where using soft bolts and sloppy holes are fine.

 

[nelstomlinson]

Years ago, I learned that when working on outdoor power equipment that I want to last is would replace every nut, bot, washer with stainless steel and I always use Nylocs. Heck, you can even get "thin" stainless Nylocs !

Stainless galls, and stainless on stainless will gall and seize in a heartbeat. If you use all stainless, assemble with anti-seize, and don't use power tools to spin the nut on or off. A galvanised nut on a stainless bolt is less likely to seize.

Stainless is also susceptible to fatigue and cracking, so be cautious about using it in high stress or high vibration applications.

 

[Leaflessshadetree]

Stainless galls, and stainless on stainless will gall and seize in a heartbeat. If you use all stainless, assemble with anti-seize, and don't use power tools to spin the nut on or off. A galvanised nut on a stainless bolt is less likely to seize.

Stainless is also susceptible to fatigue and cracking, so be cautious about using it in high stress or high vibration applications.

If both parts are the same grade of stainless they are more likely to Gall.
If the bolt and nut are different grades of stainless it is usually enough to avoid galling.

 

[gearhead1]

Used a lock washer on the air cleaner stud on my race car. Came in from feature and the stud, cover (top), and filter were gone.

Next week, I double nutted the cover, put the first nut where I wanted it, then ran the second nut down to the first and used wrenches to turn the two into each other. Came in from the track and the whole stud came out of the carb losing the cover and air cleaner yet again.

So, I put loctite on another stud and screwed it in the carb and ran a nylock nut down to where the stud goes in the carb. I also put a nylock nut to hold down the cover, then I used two pieces of duct tape in a cross pattern, poked a small hole in the center and slid down over the stud. The air cleaner no longer comes off. I always saw so many other cars with duct tape on the air cleaner, now I know why.

I use nylock nuts.

 

[Wamsutta]

As an experiment, I put a little blue Loctite onto a brand new very clean grade 8 bolt and threaded on the matching grade 8 nut. Let it sit there on the counter for 24 hours. When I came back to check it, the nut would not turn at all. Amazing stuff.

 

[L5wolvesf]

Used a lock washer on the air cleaner stud on my race car. Came in from feature and the stud, cover (top), and filter were gone.

Next week, I double nutted the cover, put the first nut where I wanted it, then ran the second nut down to the first and used wrenches to turn the two into each other. Came in from the track and the whole stud came out of the carb losing the cover and air cleaner yet again.

So, I put loctite on another stud and screwed it in the carb and ran a nylock nut down to where the stud goes in the carb. I also put a nylock nut to hold down the cover, then I used two pieces of duct tape in a cross pattern, poked a small hole in the center and slid down over the stud. The air cleaner no longer comes off. I always saw so many other cars with duct tape on the air cleaner, now I know why.

I use nylock nuts.

I had a similar situation on a race car I ran in the '80s. My move, after the stud came loose, was to locktite it to the carb and run a nut down to the carb, then a nylock to hold down the cover.

 

[jallyn]

Proper torque is a major factor in fasteners staying put. If the fastener is tightened properly, and the joint is not overstressing the fastener, they rarely work loose. If properly torqed fasteners loosen in use, the joint is improperly designed. Either the fasteners are too small, too few, too weak, or the joint itself is not designed to take the forces it experiences.

^This.

I worked for Caterpillar for a time, you know the big yellow equipment that is off-road, 24/7 heavy duty, vibrating, thermal-cycling, you name it. Do you know how many bolted joints are designed on Cat equipment? Proper torque. No lock washer, no Ny-locks, no thread locker. Just properly designed, bolt, nut, washers, and torque spec.

 

[FigureItOut]

If both parts are the same grade of stainless they are more likely to Gall.
If the bolt and nut are different grades of stainless it is usually enough to avoid galling.

Would this be true of stainless hardware with a black oxide finish?

Sent from my XT1575 using Tapatalk

 

[pstemari]

Would this be true of stainless hardware with a black oxide finish?

How does one get a black oxide finish on stainless steel?? Black oxide is basically dry rust (more precisely magnetite). Stainless steel doesn't rust because there's a clear layer of chromium and nickel oxides protecting the surface.

Sent from my Nexus 6 using Tapatalk

 

[FigureItOut]

How does one get a black oxide finish on stainless steel?? Black oxide is basically dry rust (more precisely magnetite). Stainless steel doesn't rust because there's a clear layer of chromium and nickel oxides protecting the surface.

Sent from my Nexus 6 using Tapatalk

Interesting question. I want to read some more about black oxide but the first couple things I read seem to indicate the process isn't much different than for any other steel.

http://www.swdinc.com/blackoxidebasics.html

black oxide for stainless steel is a mixture of caustic, oxidizing, and sulfur salts. It blackens 300 and 400 series, and the precipitation-hardened 17-4 PH stainless steel alloys.

Sent from my XT1575 using Tapatalk

 

[ncfh]

As to when you would not use loctite or other thread locker...

It has what one might loosely categorize as a "land based window" of vibration and other aggravated loosening resistance.

Meaning, unless used within the scope of the original design intention; in the sea or the sky, it is probably not going to end well.

It won't last in a car wash, near a pool, or similar environments. It is absolutely ruined by chlorine and fluorine.

Rooftops can be pretty harsh environments too ...I haven't seen much about weathering and UV/thermo cycling loctite. I recently did see a greenhouse dome collapse because the exposed metal fastener heads got so hot that they eventually melted through the rigid poly- panels, and a good wind ripped the whole place down. /tangent

It cannot be used in torque critical applications, as it's physical variation over short periods of time make it unpredictable, and thus not a reliable lubricant.

It cures anaerobically, and in the presence of too much oxygen it just refuses to cure. This means that if you use too much, so that it is visibly coming out and circling the exposed threads, or pooling, the inside may cure slowly, or not at all.

It is material and surface finish sensitive. It has problems bonding to some stainless steels and coatings on some hardware, even when used with their fancy primer.

Company A's SS hardware, acetone bath, red loctite cures hard, no problem.

Company B's SS equivalent hardware, same process, 48 hours later and it could still be easily undone with a wrench. Some of the red loctite itself was a still wet but hardening spiral that easily separated from both hole and fastener, totally unadhered to either.

It is "oil resistant" but not oil proof, particularly with molybdenum disulfide and possibly other dry film coatings. You would think this would be obvious, but apparently not to lots of engineers. This means always, always clean the hardware you intended to thread lock, don't just trust it will be okay.

...

Thread locker is really for internal fastening applications; think parts inside of a larger machine that there is not access to.

Through engineering laziness, a desire for reduced BOM count, less skilled workforce, etc, etc, (read: cost cutting) and again, engineering laziness, it has become the miracle-do-all-wonder of the fastening challenged everywhere.

And like any industrial product of sheer laziness, it has thus permeated into the consumer market.

But it is not "reliable" like saftey-wire or a Nord lock would be in a critical application.

I love me some Nord locks myself.

Finger tighten the ******* and you NEED a wrench to get it back off. Through bolt, with one under the head and one under the nut, amazing.

Oh, and on stainless steel hardware, we tested Loctite's fancy and expensive primer against acetone, and there was no measurable difference.

 

[earlthegoat2]

^This.

I worked for Caterpillar for a time, you know the big yellow equipment that is off-road, 24/7 heavy duty, vibrating, thermal-cycling, you name it. Do you know how many bolted joints are designed on Cat equipment? Proper torque. No lock washer, no Ny-locks, no thread locker. Just properly designed, bolt, nut, washers, and torque spec.

Cat is one of the companies I was referring to in my previous post. They use good fasteners and I never see spring type lock washers. Some of the second tier companies like to use crutches to cut costs that end up costing the customer way more in the end.